GROL Amplifier and Oscillator Circuits 2

Question 1

In a Colpitts oscillator, the frequency-determining tank circuit consists of:

Accepted Answer

Two capacitors and one inductor

Answer

The Colpitts oscillator uses a capacitive voltage divider formed by two capacitors and a single inductor as its tank circuit.

Question 2

What distinguishes a Hartley oscillator from a Colpitts oscillator?

Accepted Answer

A Hartley oscillator uses a tapped inductor in its tank circuit

Answer

The Hartley oscillator uses a tapped (center-tapped) coil as its inductive element, while the Colpitts uses two capacitors as its voltage divider.

Question 3

Why are crystal-controlled oscillators preferred in commercial radio transmitters?

Accepted Answer

They provide superior frequency stability compared to LC oscillators

Answer

Crystal oscillators exploit the piezoelectric properties of quartz to achieve very high frequency stability compared to LC circuits.

Question 4

The Barkhausen criterion states that for sustained oscillation, the total loop gain must be:

Accepted Answer

Equal to unity with a total phase shift of 0° or 360°

Answer

For sustained oscillation, the amplifier gain must exactly compensate for feedback network losses, and the total phase shift around the loop must be 0° or a multiple of 360°.

Question 5

Which oscillator circuit is commonly used with a quartz crystal because it requires only one active device and connects the crystal directly in the feedback path?

Accepted Answer

Pierce oscillator

Answer

The Pierce oscillator connects the crystal directly in the feedback path between drain and gate with minimal external components, making it very practical for crystal-controlled designs.

(GROL) General Radiotelephone Operator License Practice Test

(GROL) General Radiotelephone Operator License Practice Test

GROL Amplifier and Oscillator Circuits 2